Currently, many industries produce vast quantities of plastic material waste and are seeking ways to reduce waste. Much of this waste is in the form of plastic materials made from polyethylene and polypropylene materials. In particular, the packaging and health care industries are looking for a safe and effective way to dispose of medical packaging, infectious medical waste and medical disposable products.
Consequently, many industries are seeking new materials to replace polyethylene and/or polypropylene plastic materials. This is a special concern to the packaging and health care industries, for instance, since such industries are currently producing more and more types of disposable type products. One material considered for replacement of polyethylene and/or polypropylene materials is polyvinyl alcohol (PVOH).
There is a great deal of interest in using the water soluble polyvinyl alcohol polymers as components in many person care and medical care products such as films, sheets, nonwoven materials, woven fabrics, foams, injected molded products and thermal formed products. However, materials made of these water soluble polymers suffer from a lack of toughness, tear resistance and heat seal strength.
Various medical disposable products, such as disclosed in U.S. Pat. Nos. 5,181,966, 5,181,967 and 5,207,387, are made from externally plasticized hot water soluble polyvinyl alcohol compositions. These medical products are disposed of by being placed in a special high temperature washing machine that breaks down the polyvinyl alcohol compositions. During the process, the medical disposable materials are reduced to a fluid-like soapy liquid which then enters the sewer system. The 90.degree. C. plus high temperature of the water sterilizes the waste water before the waste water is sent along with other sewage to a water treatment facility. The breakdown products entering the sewer system in the washing machine are biodegradable and meet health standards.
However, a problem arises with such hot water soluble films and/or disposable products. These films and products often do not have good cold water resistance. In order for a product to be useful, the product must be cold water resistant for at least about six to eight hours while being in direct contact with cold water. The currently available commercial hot water soluble films are made of a solution cast or melt extruded polyvinyl alcohol film which does not have adequate cold water resistance for the time requirements needed in the health care industry. These products do not retain their integrity after about five minutes exposure to cold waters.
Attempts to develop hot water soluble PVOH films included using thermoplastic PVOH resin blends consisting of a fully hydrolyzed PVOH resin or resin blend, an external plasticizer such as glycerol and other additives. In order to work with the film, however, the film extrusion temperatures were very close to the thermal decomposition temperature of the PVOH resin. While the external plasticizer is added to reduce the extrusion temperature and improve the flexibility, the external plasticizer causes severe smoking and lensing problems during film extrusion. The resulting hot water soluble PVOH films were very brittle with low tear strength and low elongation and lack of cold water resistance. Further, these hot water soluble PVOH resins had many undesirable cross-linked polymer gels.
In addition, the water soluble films containing externally plasticized polyvinyl alcohol are not suitable for use in many disposable products. The external plasticizer additives migrate out of the polyvinyl alcohol materials. For instance, disposable products such as diapers, underpads and sanitary napkins generally comprise three major components: a topsheet, an absorbent core and a backsheet. The topsheet is usually a nonwoven fabric or a perforated film, while the backsheet is usually an embossed film or a coated nonwoven fabric. The disposable products are packaged in close arrangement in a plastic bag or box. The backsheet and topsheet are in direct contact with the absorbent core layer. If the backsheets and/or topsheets contain polyvinyl alcohol with external plasticizers, then the low molecular weight plasticizer additive in the plasticized polyvinyl alcohol films,are absorbed by the absorbent core layer. By losing most or all of the plasticizer additive, the polyvinyl alcohol film becomes brittle, weak and non-useful.
Another material considered for replacement of polyethylene and/or polypropylene material is an alkaline soluble thermoplastic resin. These alkaline soluble thermoplastic polymers are of environmental interest because of their solubility in alkaline solutions and their compostability due to eventual disintegration upon prolonged exposure to moisture, notwithstanding the fact that the films are relatively hydrophobic. However, alkaline soluble polymers are very brittle and-weak. Films and nonwovens made from these alkaline soluble polymers are also quite sticky and tend to block in roll form. In addition, stability and aesthetic properties of these material are very poor. Further, injected molded products made of alkaline soluble polymers are also very brittle. Various products containing alkaline soluble materials are described in the U.S. Pat. Nos. 4,870,148, 5,063,272, 5,149,333 and 5,346,955. These materials comprise(meth)acrylic ester/(meth)acrylic acid copolymers and modified polyolefins. However, it has been found that the polymeric web compositions made of these materials do not have the desired improved properties and the alkaline solubilities of these web is very poor. In addition, many of these products contain property modifiers which are not soluble in alkaline solutions.
It is an object of the present invention to provide composite films and articles useful for making biodegradable disposable products. The compositions provided by this invention have excellent long-term shelf life under "dry conditions", including product storage and end use periods. According to the present invention, the compositions can ultimately be dissolved or broken down in the presence of a hot alkaline solution, such as hot water with a strong detergent commonly used in a washing machine.
Another object of the present invention is to provide liquid impervious thermoplastic films which are especially suitable for use in absorbent articles such as surgical gowns, drapes, sanitary napkins, panty liners, diapers and the like, which are adapted for absorbing various bodily fluids.
Another object of the present invention is to provide liquid impervious thermoplastic degradable articles which are especially suitable for use as various medical disposable products such as biohazard bags, hospital laundry bags, liner bags, suture bags, Mayo stand covers, table covers, drape sheets, utility drapes, laparotomy sheets, CRS wraps, underpads, bed linens, drapes, gowns, needle counters, prep trays, operation room basins, bowls, sponges, utensils, petri dishes, pipettes, specimen containers, medicine cups, glasses and the like which come into contact with various bodily fluids.
It is another object of the present invention to provide a degradable molded product and thermoformed product useful for packaging applications such as for packaging insecticides, medicines, chemicals, dyes, pigments and industrial additives and similar materials.